Storing energy and powering small systems with mechanical springs made of carbon nanotube yarn

CNT (carbon nanotube) yarns stretched in tension as mechanical springs are used to drive both electrical and mechanical loads in order to demonstrate the CNT yarns' potential for high power density, their potential for metered energy release, and their application to power practical systems. The energy-storing properties of the CNT yarn are characterized, and the design, operation, and characterization of three demonstration systems that store energy in stretched CNT yarns and release it to drive an electrical or mechanical load are presented. When loaded in tension, the yarn stores energy with an energy per unit length of up to 13.4 mJ/m and an energy density of up to 7720 kJ/m 3 or 6.7 kJ/kg. The CNT spring-driven demonstration systems include a mechanical slingshot and two mechanically-driven electric power supplies. The slingshot releases energy stored in a stretched CNT spring rapidly to launch a projectile, with up to 56% power extraction efficiency. The first electric power supply converts stored mechanical energy into electric power using an escapement-based power regulation mechanism and piezoelectric energy conversion. The second electric power supply uses an electromagnetic conversion system to convert energy stored in the CNT spring to electric output power without regulating the rate of energy release from the spring. The devices demonstrate that CNT yarn can be used to drive mechanical and electrical loads using both quick-release devices that provide high power, and slow-release, escapement-metered systems.